This application is a renewal application in competition for CREG program DCCP 1, Replication of RNA Tumor Viruses. The objectives of this proposed research are: (1) investigation of RNA-directed DNA polymerization in vitro and the coupled role of DNA polymerase and ribonuclease H activities using purified AMV DNA polymerase and 35S viral RNA subunits; (2) isolation and characterization of additional factors and enzymes from virus particles and/or virus-infected cells involved in reverse transcription of AMV RNA; and (3) reconstitution of a viral RNA-directed DNA complex synthesizing viral DNA analogous to that found in the infected cell.